tdlight/tdutils/td/utils/FloodControlStrict.h

//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2022
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#pragma once

#include "td/utils/common.h"

#include <limits>

namespace td {

// More strict implementaions of flood control than FloodControlFast.
// Should be just fine for small counters.
class FloodControlStrict {
 public:
  // there is no reason to return wakeup_at_, because it will be a time before the next allowed event, not current
  void add_event(double now) {
    events_.push_back(Event{now});
    if (without_update_ > 0) {
      without_update_--;
    } else {
      update(now);
    }
  }

  // no more than count in each duration
  void add_limit(int32 duration, size_t count) {
    limits_.push_back(Limit{duration, count, 0});
    without_update_ = 0;
  }

  double get_wakeup_at() const {
    return wakeup_at_;
  }

  void clear_events() {
    events_.clear();
    for (auto &limit : limits_) {
      limit.pos_ = 0;
    }
    without_update_ = 0;
    wakeup_at_ = 0.0;
  }

 private:
  void update(double now) {
    size_t min_pos = events_.size();

    without_update_ = std::numeric_limits<size_t>::max();
    for (auto &limit : limits_) {
      if (limit.count_ < events_.size() - limit.pos_) {
        limit.pos_ = events_.size() - limit.count_;
      }

      // binary-search? :D
      auto end_time = now - limit.duration_;
      while (limit.pos_ < events_.size() && events_[limit.pos_].timestamp_ < end_time) {
        limit.pos_++;
      }

      if (limit.count_ + limit.pos_ <= events_.size()) {
        CHECK(limit.count_ + limit.pos_ == events_.size());
        wakeup_at_ = max(wakeup_at_, events_[limit.pos_].timestamp_ + limit.duration_);
        without_update_ = 0;
      } else {
        without_update_ = min(without_update_, limit.count_ + limit.pos_ - events_.size() - 1);
      }

      min_pos = min(min_pos, limit.pos_);
    }

    if (min_pos * 2 > events_.size()) {
      for (auto &limit : limits_) {
        limit.pos_ -= min_pos;
      }
      events_.erase(events_.begin(), events_.begin() + min_pos);
    }
  }

  double wakeup_at_ = 0.0;
  struct Event {
    double timestamp_;
  };
  struct Limit {
    int32 duration_;
    size_t count_;
    size_t pos_;
  };
  size_t without_update_ = 0;
  vector<Event> events_;
  vector<Limit> limits_;
};

}  // namespace td